Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$231.47	9.632%	$253.7652	$253.77	$253.75	$253.80
Purchase #2	$185.74	11.767%	$207.596	$207.60	$207.60	$207.60
Purchase #3	$96.27	9.654%	$105.5639	$105.56	$105.55	$105.60
Purchase #4	$80.58	13.322%	$91.3149	$91.31	$91.30	$91.30
Purchase #5	$131.46	7.393%	$141.1788	$141.18	$141.20	$141.20
Purchase #6	$230.83	10.390%	$254.8132	$254.81	$254.80	$254.80
Purchase #7	$41.87	7.218%	$44.8922	$44.89	$44.90	$44.90
7 purchase totals =	$998.22		$1,099.1242	$1,099.12	$1,099.10	$1,099.20